All passwords, which are set in web.config have to be encrypted.
Therefore navigate to the tool „PasswordEncryptor.exe“, which is shipped with the WebOffice10R3-DVD and can be found in the following directory „Software/UserManagement Admin Web/PasswordEndcryption“.
Open the tool, enter the original password in plaintext and click at the “Verschlüsseln” button to get the encrypted password.

Password Encryptor